/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * mm/mm_heap/mm_shrinkchunk.c
 *
 *   Copyright (C) 2007, 2009, 1013 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <tinyara/mm/mm.h>

#include "mm_node.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/****************************************************************************
 * Global Functions
 ****************************************************************************/

/****************************************************************************
 * Name: mm_shrinkchunk
 *
 * Description:
 *   Reduce the size of the chunk specified by the node structure to the
 *   specified size.  this internal logic is used both from memalign to
 *   dispose of any trailing memory in the aligned allocation and also by
 *   realloc when there is a request to reduce the size of an allocation.
 *
 *   NOTES:
 *     (1) size is the whole chunk size (payload and header)
 *     (2) the caller must hold the MM semaphore.
 *
 ****************************************************************************/

void mm_shrinkchunk(FAR struct mm_heap_s *heap, FAR struct mm_allocnode_s *node, size_t size)
{
	FAR struct mm_freenode_s *next;

	/* Get a reference to the next node */

	next = (FAR struct mm_freenode_s *)((char *)node + node->size);

	/* Check if it is free */

	if ((next->preceding & MM_ALLOC_BIT) == 0) {
		FAR struct mm_allocnode_s *andbeyond;
		FAR struct mm_freenode_s *newnode;

		/* Get the chunk next the next node (which could be the tail chunk) */

		andbeyond = (FAR struct mm_allocnode_s *)((char *)next + next->size);

		/* Remove the next node.  There must be a predecessor, but there may
		 * not be a successor node.
		 */

		REMOVE_NODE_FROM_LIST(next);

		/* Create a new chunk that will hold both the next chunk and the
		 * tailing memory from the aligned chunk.
		 */

		newnode = (FAR struct mm_freenode_s *)((char *)node + size);

		/* Set up the size of the new node */

		newnode->size        = next->size + node->size - size;
		newnode->preceding   = size;
		node->size           = size;
		andbeyond->preceding = newnode->size | (andbeyond->preceding & MM_ALLOC_BIT);

		/* Add the new node to the freenodelist */

		mm_addfreechunk(heap, newnode);
	}

	/* The next chunk is allocated.  Try to free the end portion at the end
	 * chunk to be shrunk.
	 */

	else if (node->size >= size + SIZEOF_MM_FREENODE) {
		FAR struct mm_freenode_s *newnode;

		/* Create a new chunk that will hold both the next chunk and the
		 * tailing memory from the aligned chunk.
		 */

		newnode = (FAR struct mm_freenode_s *)((char *)node + size);

		/* Set up the size of the new node */

		newnode->size      = node->size - size;
		newnode->preceding = size;
		node->size         = size;
		next->preceding    = newnode->size | MM_ALLOC_BIT;

		/* Add the new node to the freenodelist */

		mm_addfreechunk(heap, newnode);
	}
}
